Increase of desulphurization potential of technological systems of hot metal injection desulphurization by various reagents

Abstract

Last years the requirements considerably increased to the processes of liquid hot metal preparation to steel-making stage. However, analysis of the industrial application practice of hot metal desulphurization different technologies shows often their insufficient effectiveness. It was shown, that the used technologies have reserves for significant increasing desulphurization indices, including the increase due to optimization of thermodynamics conditions, kinetics and hydro- and air-dynamics of exchanging processes. Calculations of Gibbs energy values variations carried out for various hot metal temperature in interaction reactions of basic reagents with Sulphur. It was shown, that calcium oxide and magnesium are the most preferable reagents for hot metal desulphurization, since they provide the highest values (absolute) of Gibbs energy variation. Magnesium interaction with the Sulphur dissolved in the hot metal, tales place not only in the area of its injection into the melt, but also in the whole volume of the bath under refining, which is stipulated by the ability of magnesium dissolving in the hot metal. At the calcium oxide injection it is necessary to arrange the chemical interaction with the introduced from outside aluminum, as well as destruction and dispersion of flow discharge zone out of the lance into the hot metal, by gas-forming additives. In the case of mono-injection of magnesium, it is important to ensure a granular composition of the reagent and a high (more than 80 m/s) flow rate into the hot metal. At injection granular reagents with particle diameters of more than 0.4 mm, the velocity parameter is decisive, since it provides the possibility of introducing reagent particles into the hot metal to a depth of up to 20–25 mm. The latter provides stability and reliability of the hot metal desulphurization process by mono-injection of granular magnesium. Theoretical conclusions were confirmed by experiments. The degree of desulphurization was up to 95–99%.